Closure and system for NMR sample containers with a secondary locking seal

ABSTRACT

A selectively removable closure for closing the open end of an NMR sample tube having an open end and a closed end of the invention includes a cylindrical proximal first and a distal second portion, both portions substantially congruent to a central axis, the second portion has a hollow bore extending therethrough, the hollow bore has: a first and a second distal section, a central section and a proximal section. The first distal section has an inside diameter sized to accept the outside diameter of a preselected size NMR sample tube substantially without an interference, the second distal section has an interference that ends into the central section with a ramp with an angle to the central axis greater than 70 degrees, the central section corresponds in a locked position on the NMR sample tube with a locking ring at least partially surrounding the NMR locking tube to form a secondary locking seal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/739,753 filed Jun. 15, 2015, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

This application is generally related to sample containers for placing asample for measurement of a property of the sample in an instrument, andmore particularly, to closure devices and tubes for a Nuclear MagneticResonance (NMR) samples with a secondary locking seal.

BACKGROUND

Nuclear Magnetic Resonance spectrometry is widely used in chemicalstudies for structure determination as well as presence, absence orconcentration of a particular component in a sample. An NMR spectrum ofa sample is generally determined by placing the sample in an elongatesample tube, placing the tube containing the sample in the field of apowerful magnet and selectively irradiating the sample with preselectedradiofrequency signals and recording the effects of these signals on thesample. The sample tubes are formed from glass and are supplied inseveral sizes ranging from diameters of 1 mm to about 10 mm with lengthsof about four inches to about seven inches long. The resolution of thespectrometer may be adversely affected by asymmetries in the sample tubeand its placement within the magnetic field and irradiation coils.Accordingly, users of NMR spectrometers seek sample tubes and holdersthat minimize asymmetry.

In an effort to “average-out” sample asymmetry, some spectrometersaxially spin samples on which the spectrum is being determined. Morerecently, NMR spectrometers have the capability to average-out somesample asymmetry electronically without spinning, but sample placementand positioning in the sample chamber is still important to optimize theresolution of the spectrometer. These more recent NMR spectrometers alsoutilize the tube closure to suspend the sample axially in the samplechamber. Thus, tube closures or caps need to do more than just close thetube. When the samples are not spun, the coaxiality of the outerdiameter, the closure and the inside diameter of the tube, if notconsistent and precise, may adversely effect the quality of the spectrumobtained.

In many cases, the materials whose NMR spectrum is being determined arederived from expensive and difficult to repeat studies. Accordingly, ifa sample is lost or degraded because of a malfunction of the sampleclosure or the tube, the user may experience a substantial and expensivedelay in their study. Thus, although there are many types of NMR samplesystems and tube closure devices available, there is still a need for anNMR sample system and closure which is reliable, simple to use andallows the user of an NMR spectrometer to fully utilize the resolutioncapability of the spectrometer. If such a device also was compatiblewith available automated sample handling equipment, a further benefit tothe art of NMR spectrum determination would be realized. Such a systemand closure is disclosed herein.

SUMMARY

A selectively removable closure for closing the open end of an NMRsample tube having an open end and a closed end includes a cylindricalproximal first and a distal second portion, both portions beingsubstantially congruent to a central axis thereof. The second portionhas a hollow bore extending therethrough. The hollow bore has threesections: a distal section; a central section; and a proximal section.The distal section has an inside diameter sized to accept the outsidediameter of a preselected size NMR sample tube substantially without aninterference. The central section is sized to provide a compliantinterference fit with the outside diameter of the preselected size NMRsample tube. The proximal section is sized to accept the outsidediameter of the preselected size NMR sample tube without interference,so that as the open end of the NMR sample tube is proximally axiallyinserted into the closure, the distal section guides the tube into theclosure, the central section interference fit provides a userperceptible resilient resistance to the axial passage of the tube andthe movement of the tube open end into the proximal section allows theuser to perceive a lessened resistance of the movement of the tubefollowed by seating the tube open end substantially adjacent to thefirst portion of the closure.

A method for manufacturing a closure includes selecting a polymericmaterial in the form of an elongate cylinder; placing the elongatecylinder of the polymeric material in a lathe; shaping the elongatecylinder into a closure having a cylindrical proximal first and a distalsecond portion, both portions being substantially congruent to a centralaxis thereof, the second portion having a hollow bore extendingtherethrough, the hollow bore having a distal section, a central sectionand a proximal section, the distal section having an inside diametersized to accept the outside diameter of a preselected size NMR sampletube substantially without an interference, the central section sized toprovide a compliant interference fit with the outside diameter of thepreselected size NMR sample tube, and the proximal section sized toaccept the outside diameter of the preselected size NMR sample tubewithout interference; and removing the finished closure from the lathe.

A method for determining the NMR spectrum of a material includes placingan aliquot of a suitable solvent containing a sufficient amount of amaterial of which an NMR spectrum is to be determined in a preselectedsize NMR sample tube having an open end and a closed end defining acavity for receiving the aliquot; applying a closure to the open end ofthe NMR tube, the closure having a cylindrical proximal first and adistal second portion, both portions being substantially congruent to acentral axis thereof, the second portion having a hollow bore extendingtherethrough, the hollow bore having a distal section, a central sectionand a proximal section, the distal section having an inside diametersized to accept the outside diameter of the preselected size NMR sampletube substantially without an interference, the central section sized toprovide a compliant interference fit with the outside diameter of thepreselected size NMR sample tube, and the proximal section sized toaccept the outside diameter of the preselected size NMR sample tubewithout interference so that the open end of tube is disposed adjacentto the first portion of the closure; grasping the closure picking up thesample tube having the material therein; placing the closed sample tubeinto a sample cavity of an NMR spectrometer; and operating the NMRspectrometer to determine the spectrum of the material.

The closure and sample tube system of the invention provides users ofNMR spectrometers with a selectively removable closure for NMR sampletubes which is easily and securely placed on the tube. The closure ofthe invention maintains a seal, even if the open end of the tube ischipped or not square, because it does not depend on the extreme top ofthe tube for the retention and seal of the tube. In some embodiments,the system of the invention incorporates the closure of the inventioncooperatively sealingly engaging an area of reduced outside diameter ofthe tube. In substantially all of the embodiments, the closure of theinvention enables the user to grasp the cap for picking up and placingthe tube without worrying that the cap may separate from the tube andcause the sample to be lost. Additionally, some embodiments of theclosure and sample tube system of the invention may be utilized withvarious available auto sampling systems.

One or more embodiments of the present invention provide a removableclosure for closing an open end of an NMR sample tube. The NMR sampletube having an open end, a closed end, and an outside diameter. Theclosure may comprise a cylindrical proximal first portion and a distalsecond portion, both portions being substantially congruent to a centralaxis thereof. The first portion may have a closed end and the secondportion defining a hollow bore extending therethrough. The hollow boremay have a first distal section, a second distal section, a centralsection and a proximal section, the first distal section having afurther distance to the proximal section than the second distal section.The first distal section may have an open end with an inside diametersized to accept the NMR sample tube. The first distal section may havean inside diameter decreasing towards the second distal section andforming an increasing interference with the NMR sample tube. The firstdistal section may end with an increase in the inside diameter of theremovable closure of at least 0.003 inch to transit into a beginning ofthe second distal section, the inside diameter of the second distalsection increasing toward the closed end with an angle that is greaterthan 70 degrees relative to the central axis. The second distal sectionmay have an open end with an inside diameter sized to accept the NMRsample tube substantially without interference, the central sectionbeing tapered and sized to provide a compliant interference fit with theoutside diameter of the NMR sample tube, and the proximal section beingnear the proximal first portion, being tapered and being sized to acceptthe outside diameter of the NMR sample tube without interference.

Other embodiments of the present invention may provide a NMR sample tubehaving a locking ring at least partially surrounding the outsidediameter of the NMR sample tube. The locking ring may be at a positionthat coincides with a position of the second distal section of theremovable closure closing the NMR sample tube in a closed position.Embodiments of the invention may comprise a locking ring of materialdeposited on the outside of the NMR sample tube. That material maycomprise ink.

In one or more embodiments of the present invention, the material thatis deposited on the outside of the NMR tube is deposited by a screenprinting process.

In various embodiments, the NMR sample tube has a marking regioncontaining a mark with an edge that determined the position of thelocking ring.

The material deposited on the NMR tube, such as the material of thelocking ring, may have a thickness after being cured in the range of0.0002 inches to 0.0003 inches. Various embodiments of the invention mayhave a locking ring width of 0.028 inches centered at a distance of0.144 inches from the open end of the NMR tube. In other embodiments,the NMR tube does not comprise a locking ring.

In one or more embodiments, the removable closure may be made of lowdensity polyethylene (LDPE).

One or more embodiments of the present invention provide a spectroscopyapparatus comprising a Nuclear Magnetic Resonance spectroscopy (NMR)sample tube with a material deposited on the outside surface of the NMRsample tube as one or more bands spanning more than ¼ of thecircumference of the NMR sample tube. In one or more embodiments, theNMR sample tube has a length of approximately 7 inches and at least partof the one or more bands is located at one or more of the followingpositions on the NMR sample tube: 2.7755 inches above the closed end ofthe sample tube; 4.5465 inches above the closed end of the sample tube;5.750 inches above the closed end of the sample tube; 6.25 inches abovethe closed end of the sample tube.

In one or more embodiments, the material deposited on the outside of theNMR sample tube has a friction coefficient of greater than 0.15. Furtherembodiments of the present inventions may comprise one or more band thatare continuous or discontinuous. The one or more bands of depositedmaterial may be approximately 0.669 inches wide relative to the lengthof the sample tube, and may be deposited with a thickness ofapproximately 0.00025 inches.

Alternative embodiments of the present invention provide a material thatis deposited on the outside of an NMR tube, wherein the materialcomprises an epoxy based screen printing ink, from 70 to 97% w/w; acatalyst, from 3 to 10% w/w; and a silica filler, from 0 to 20% w/w. Inyet other embodiments, the epoxy based screen printing ink comprisesabout 93.8% w/w; the catalyst comprises about 3.6% w/w; and the silicafiller comprises about 2.6% w/w.

Various embodiments of the present invention provide curing the materialthat is deposited on the outside of the NMR tube without discolorationof the ink. One embodiment provides the deposited material cures withoutany discoloration of the ink perceivable to the human eye after beingheated to about 250 degrees F. for about 3 minutes. In otherembodiments, the epoxy based screen printing ink is white with noyellowing perceivable to the human eye after being heated to about 250degrees F. for about 3 minutes.

One or more embodiments of the present invention provide a spectroscopysystem comprising a Nuclear Magnetic Resonance spectroscopy (NMR) sampletube having an open end and a closed end and a turbine having a proximalend and a distal end, the turbine defining a hollow bore from theproximal end to the distal end of the turbine, the NMR sample tubeseated inside the hollow bore with closed and open ends positionedoutside the hollow bore, the turbine having a first contact position inthe proximal half of the turbine and a second contact position in thedistal half of the turbine, the first and second contact position beinglocated approximately 1.771 inches apart. The NMR sample tube may have amaterial deposited on the outside surface as two bands spanning morethan ¼ of the circumference of the NMR sample tube, wherein the firstcontact point touches at least part of one of the two bands while,simultaneously, the second contact point touches at least part of theother of the two bands.

In various embodiments, one or more edges of the two bands line up withthe proximal or distal end of the turbine and/or line up with the firstor second contact position of the turbine.

In other embodiments, a removable closure, as described above, mayfurther comprise an NMR sample tube with the closure seated on the openend of the NMR sample tube. The internal diameter of the closure may beincreased relative to a starting diameter by exposure to a solvent vaporfor 1.5 hours, wherein the closure maintains seating on the open end ofthe NMR sample tube while the closure and sample tube are liftedvertically by only the closure, with the closure and NMR sample tubealigned vertically.

In yet other embodiments, the removable closure as described above, maybe seated on the open end of the NMR sample tube, wherein the internaldiameter of the closure is increased relative to a starting diameter byexposure to a solvent vapor for more than 1.5 hours and the closuremaintains seating on the open end of the NMR sample tube while theclosure and sample tube are lifted vertically by only the closure, withthe closure and NMR sample tube aligned vertically.

In yet other embodiments, the removable closure described above furthercomprises an NMR sample tube, the closure seated on the open end of theNMR sample tube, wherein the internal diameter of the closure isincreased 0.16% relative to a starting diameter by exposure to a solventvapor, with the closure maintaining seating on the open end of the NMRsample tube while the closure and sample tube are lifted vertically byonly the closure, with the closure and NMR sample tube alignedvertically.

In yet other embodiments, the removable closure described above may beseated on the open end of the NMR sample tube, wherein the internaldiameter of the closure is increased greater than or equal to 0.16%relative to a starting diameter by exposure to a solvent vapor, and theclosure maintains seating on the open end of the NMR sample tube whilethe closure and sample tube are lifted vertically by only the closure,with the closure and NMR sample tube aligned vertically.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded partial cross-sectional perspective view of oneembodiment of the closure of the invention with an NMR sample tube.

FIG. 2 is a cross-sectional view of an embodiment of the closure of theinvention with dimensions appropriate for an NMR tube having a nominal 4mm outside diameter.

FIG. 3 is a cross-sectional view of an embodiment of the closure of theinvention with dimensions appropriate for an NMR tube having a nominal 5mm outside diameter.

FIG. 4 is a cross-sectional view of another embodiment of the closure ofthe invention with dimensions appropriate for an NMR tube having anominal 5 mm outside diameter.

FIG. 5 is a cross-sectional view of another embodiment of the closure ofthe invention with dimensions appropriate for an NMR tube having anominal 3 mm outside diameter.

FIG. 6 is an exploded cross-sectional view of another embodiment of theclosure of the invention with dimensions appropriate for an NMR tubehaving a nominal 5 mm outside diameter.

FIG. 7 is a cross-sectional view of another embodiment of the closure ofthe invention with dimensions appropriate for an NMR tube having anominal 5 mm outside diameter.

FIG. 8 is an exploded partial cross-sectional view of an embodiment of asample tube system of the invention.

FIG. 9 is a cross-sectional view of an embodiment of the closure thatidentifies a location of the first and the second distal section.

FIG. 10 is a cross-sectional view of an embodiment of the closure with asecondary locking seal in accordance with an aspect of the presentinvention.

FIG. 11 is a detailed illustration of a part of the enclosure of FIG.10.

FIG. 12 illustrates the NMR sample tube with a marking area and alocking ring in accordance with an aspect of the present invention.

FIG. 13 is a side view schematic of an NMR tube showing placement ofscreen printed bands according to one embodiment of the presentinvention.

FIG. 14 is a side view schematic of an NMR tube showing placement ofscreen printed bands according to one embodiment of the presentinvention.

FIG. 15 is a side view schematic of an NMR tube showing placement ofscreen printed bands according to one embodiment of the presentinvention.

FIG. 16 is a side view of a turbine and a NMR tube according to oneembodiment of the present invention.

FIG. 17 is a side view of a NMR tube inserted in a turbine, according toone embodiment of the present invention.

FIG. 18 is an above perspective view of an NMR tube inserted in aturbine, according to one embodiment of the present invention.

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced orbeing carried out in various ways.

DETAILED DESCRIPTION

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment”, means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment”, in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments. In this description, the term “proximal” refers to thedirection away from the closed end of the sample tube and the term“distal” refers to the direction toward the closed end of the sampletube.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present invention without departing from the spirit andscope of the invention. In particular, those skilled in the art willknow how to make appropriate changes to the dimensions of thebelow-described closure consistent with the invention and needs of theuser. Thus, it is intended that the present invention includemodifications and variations that are within the scope of the appendedclaims and their equivalents.

Referring to FIGS. 1, 2 and 3, in one embodiment, a selectivelyremovable closure 10 for closing an open end 12 of an NMR sample tube 14includes a cylindrical proximal first portion 16 and a distal secondportion 18. Both portions 16 and 18 are substantially congruent to acentral axis “X”. Second portion 18 has a hollow bore 20 extendingtherethrough. Hollow bore 20 has three sections, a distal section 22, acentral section 24 and a proximal section 26. Distal section 22 has aninside diameter m, best seen in FIG. 3, that is sized to accept theoutside diameter of a preselected size NMR sample tube substantiallywithout an interference, e.g., when a 5 mm tube is selected, having anO.D. of about 4.95±0.013 mm, I.D. “m” is about 4.98±0.025 mm. Centralsection 24 is sized to provide a compliant interference fit with theoutside diameter of the preselected NMR sample tube, e.g., for a 5 mmtube having an O.D. of about 4.95±0.013 mm, I.D. “n” is about 4.77±0.025mm. Proximal section 26 is sized to accept the outside diameter of thepreselected NMR sample tube, e.g. for a 5 mm tube having an O.D. ofabout 4.95±0.013 mm, I.D. “o” is about 5 mm. By having the several I.D.dimensions of sections 22, 24 and 26 as described above, when open end12 of sample tube 14 is proximally axially inserted into closure 10,distal section 22 guides tube 14 into the closure, central section 24provides a user perceptible resistance to passage of tube 14 and themovement of the tube into proximal section 26 allows the user toperceive a lessened resistance to the movement of the tube followed byseating open end 12 substantially adjacent first portion 16.

In some embodiments, second portion hollow bore central section 24 hasan inside diameter sized to have an interference fit of between about 2%and about 8% relative to the outside diameter of NMR sample tube 14 whenclosure 10 is placed on open end 12 of the tube. Other interference fitswhich do not damage the sample tube can be used consistent with theinvention. This interference fit serves to align tube 14 substantiallycoaxially with axis “X” of closure 10 and substantially optimallyposition the tube in the NMR sample chamber when closure 10 is beingused to suspend the tube in the sample chamber.

In one embodiment, shown in FIG. 3, where closure 10 is sized for the 5mm tube, a transition between distal section 22 and central section 24of hollow bore 20 is a ramp 30 with a slope of between about 5° to about15° relative to the distal section. In this embodiment, the transition32 between central section 24 and proximal section 26 has a slope ofbetween about −2° to about −5° relative to central section 24. Again,other transition dimensions which provide appropriate interferencewithout damaging the sample tube can be used consistent with theinvention. Yet other values for the transitions and the amount ofinterference fit may also be advantageously used for embodiments relatedto FIG. 8.

In the embodiment illustrated in FIG. 3, first portion 16 has a largeroutside diameter than second portion 18. In other embodiments,illustrated in FIGS. 4 and 5, first portion 16 and second portion 18 mayhave substantially the same outside diameters, with an additionalstructural feature such as one or more annular grooves 40 disposedsubstantially symmetrically to axis “X” along the outside diameter ofclosure 10. The distal second portion 18 of FIG. 4 has an expandedoutside diameter portion 42.

Referring to FIG. 6, in another embodiment of closure 10, first portion16 and second portion 18 may have substantially the same outsidediameters, but are individually formed as separate articles ofmanufacture. In this embodiment, first portion 16 has a hollow passage21 therethrough disposed substantially coaxially with the “X” axis ofclosure 10 and is fluidly communicative with hollow bore 20 of thesecond portion when the first portion is attached to the second portion.In this embodiment, the attachment of first portion 16 to second portion18 may be by cooperating threads, snap fit, press fit, adhesive bonding,solvent bonding, heat bonding, spin welding, sonic welding or otherforms of forming releasable or fixed attachments as may be suitable forparticular materials used to form the portions of closure 10.Additionally, as is shown in FIG. 6, there may be an enlargement 23 ineither hollow passage 21, hollow bore 20, or partially in both passage21 or bore 20 for accommodating a septum 25 formed from a resilientmaterial that would occlude passage 21 and hollow bore 20, whileallowing materials to be added or withdrawn from sample tube 14 bypenetration of septum 25 by a penetrating element such as a syringeneedle or an automated delivery device. Septum 25 is shown both adjacentto closure 10 and in phantom in enlargement 23. Suitable resilientmaterials for forming septum 25 include, but are not limited to, naturalor synthetic rubber, silicone rubber, or the like, which willsubstantially reseal after a penetration. In some embodiments, septum 25may include a slit, (not shown) to facilitate passage and withdrawal ofthe penetrating element. In this embodiment, the outside dimensions offirst portion 16 and second portion 18 are constructed so as to producegroove 40 substantially symmetrically about axis “X” when the first andsecond portions are attached.

FIG. 7 illustrates an embodiment of the closure of the invention that isdimensioned for compatibility with a robotic sampling device thatutilizes a clamp mechanism that surrounds the cap, grasps it and thenutilizes the cap to pick and place the tube. This embodiment, elementshaving similar structure and function of closure 10 in the embodimentsillustration has reference numbers similar to those of FIGS. 1-6 exceptin the 100 series. Closure 110 has a proximal first portion 116 and adistal second portion 118. Closure 110 of the invention has asubstantially uniform outside diameter over its length with a hollowbore 120 therethrough. Closure 110 has a distal section 122 withsubstantially no interference with the outside diameter of thepreselected size tube. A ramp 130 connects distal section 122 to centralsection 124. Central section 124 has a similar interference fit to thatof the embodiments described above and proximal section 126 provides theuser with a perceptible reduced resistance movement for the tube to beseated substantially adjacent proximal first portion 116.

FIG. 8 illustrates an embodiment of the closure of the invention thatcooperatively engages with an NMR sample tube to form a vessel andclosure system. In this embodiment, elements having similar structureand function of closure 10 and sample tube 14 in the embodimentsillustrated in FIGS. 1-6 are assigned similar reference numbers in the200 series. A selectively removable closure 210 for closing an open end212 of an NMR sample tube 214 includes a cylindrical proximal firstportion 216 and a distal second portion 218. Both portions 216 and 218are substantially congruent to a central axis “X”. Second portion 218has a hollow bore 220 extending therethrough. Hollow bore 220 has threesections, a distal section 222, a central section 224 and a proximalsection 226. Distal section 222 has an inside diameter m, similar tothat shown in FIGS. 1-3 for the closure 10, that is sized to accept theopen end outside diameter of a preselected size NMR sample tubesubstantially without an interference, e.g., when a 5 mm tube isselected, having an O.D. of about 4.95±0.013 mm, I.D. “m” is about4.98±0.025 mm. In the embodiment shown in FIG. 8, central section 224 issized to provide a cooperative fit with a reduced outside diameterportion 250 disposed adjacent the open end 212 of an embodiment ofpreselected NMR sample tube 214 of the invention disposed to cooperatewith central section 224 of closure 210 when the closure is fullyengaged with sample tube 214 and open end 212 abuts proximal firstportion 216 of the closure. In this embodiment, e.g., for a 5 mm tubehaving an O.D. of about 4.95±0.013 mm, I.D. “n” is about 4.77±0.025 mm,reduced outside diameter portion may have an O.D. “p” of about4.77±0.025 mm so as to provide a nominal to slight interference fit asthe open end of the tube with O.D of about 4.95±0.013 mm leaves thecentral section 224 and top portion 216.

As described above, reduced O.D. portion 250 of sample tube 214 ispositioned to cooperate with central section 224. In order to cooperatewith central section 224, a cross-sectional profile of reduced O.D.portion 250 is substantially a mirror image of the profile described fordistal section, central section 24, ramp 30 and proximal section 26 inFIGS. 1-3 above. In the embodiments with reduced O.D. portion 250, thepresence of the reduced O.D. of tube 214 will provide an interferencefit at the lower end of the range expected for the interference fitbetween central section 24 and the O.D. of tube 14 of FIGS. 1-3 withoutthe reduced O.D. section 250.

Proximal section 226 is sized to accept the outside diameter of thepreselected NMR sample tube, e.g. for a 5 mm tube having an O.D. ofabout 4.95±0.013 mm, I.D. “o” is about 5 mm. By having the several I.D.dimensions of sections 222, 224 and 226 as described above, when openend 212 of sample tube 214 is proximally axially inserted into closure210, distal section 222 guides tube 214 into the closure, centralsection 224 provides a user perceptible resistance to passage of tube214 and the movement of open end 212 of tube 214 into proximal section226 allows the user to perceive a lessened resistance to the movement ofthe tube as central section 224 cooperatively enters reduced outsidediameter portion 250 of tube 214 followed by seating open end 212substantially adjacent first portion 216. The particular dimensions andthe interference relationships of reduced O.D. portion 250 and centralsection 224 advantageously may be adjusted for sizes other than the 5 mmtube used as an example. These other embodiments encompassing otherdimensioned sample tubes and closures are to be considered within thescope of the present disclosure.

In some embodiments of the closure of the invention, the closure may beformed from a solid rod of a polymeric material such aspolytetrafluoroethylene (PTFE) or other substantially chemically inertmaterials having similar properties. The use of PTFE as a material isfacilitated by shaping the rod into the desired dimensions with acomputer numerical controlled (CNC) automated lathe apparatus. Once theCNC apparatus is properly set-up, it can repeatedly efficiently producethe closure of the invention with a high degree of accuracy andprecision. For other applications, injection molding techniques usingother polymeric materials may be utilized, but many polymeric materialssuitable for injection molding may not have the same degree of solventresistance and dimensional stability as PTFE. Additionally, PTFE hassufficient resiliency that the closure will deflect sufficiently atcentral portion 24 to allow for some variation in NMR tube outsidediameter. For example, tubes of European manufacture may have a slightlylarger nominal outside diameter for a particular size than tubesmanufactured in North America.

NMR tubes typically are formed from a vitreous material, generallyvarious types of glass, e.g., soda-lime, borosilicate, quartz, and thelike. In some applications, a polymeric material may also be used.Conventional closures are formed from polymeric materials that are morerigid than PTFE and, since these conventional tubes depend upon contactat the top of the tube to retain the closure onto the tube, the edge ofthe tube may remove material from the closure as tubes are repeatedlyinserted into the closure, which reduces the ability of the closure tobe retained on the tube. Closures 10, 110 and 210 of the inventionsubstantially avoid this problem by having a resilient interference fitbelow the top of the tube and thus are not dependent on the tube endbeing perfectly formed to seal and retain the tube in the closure.

In the embodiment of the closure and tube system illustrated in FIG. 8,reduced O.D. portion 250 may be incorporated into tube 214 byapplication of sufficient heat to soften the area where it is desired toposition reduced portion 250 while tube 214 is fixtured, thereby causinga narrowing of the tubing. In some embodiments, this procedure may beadvantageously conducted before tube 214 is cut to its final length.Alternatively, sufficient heat may be applied to tube 214 while the tubeis mounted in a lathe, and a tool, such a heated metal device or agraphite rod or paddle may be applied to the heated tube while it isrotating to achieve the desired shape of reduced O.D. portion 250.

A further benefit of the embodiments of the invention is that nominalfour inch tubes designed for use in automated sample handling devices ofdifferent manufacturers are actually produced in a separate length foreach manufacturer using their specific conventional closures. Onemanufacturer may supply tubes with closures thereon having an overalllength of 105.8±0.5 mm, while another may supply tubes with closuresthereon having an overall length of 107.5±0.2 mm. With the embodimentsof the closures of the present invention, a standardized overall tubelength of 103.5±0.2 mm may be used, with the embodiments of the closureof the present invention providing the compatible overall length for usewith current automated handling systems and NMR spectrometers.

In the embodiment of the closure and tube system illustrated in FIG. 8,reduced O.D. portion 250 may be incorporated into tube 214 byapplication of sufficient heat to soften the area where it is desired toposition reduced portion 250 while tube 214 is fixtured, thereby causinga narrowing of the tubing. In some embodiments, this procedure may beadvantageously conducted before tube 214 is cut to its final length.Alternatively, sufficient heat may be applied to tube 214 while the tubeis mounted in a lathe, and a tool, such a heated metal device or agraphite rod or paddle may be applied to the heated tube while it isrotating to achieve the desired shape of reduced O.D. portion 250.

A further benefit of the embodiments of the invention is that nominalfour inch tubes designed for use in automated sample handling devices ofdifferent manufacturers are actually produced in a separate length foreach manufacturer using their specific conventional closures. Onemanufacturer may supply tubes with closures thereon having an overalllength of 105.8±0.5 mm, while another may supply tubes with closuresthereon having an overall length of 107.5±0.2 mm. With the embodimentsof the closures of the present invention, a standardized overall tubelength of 103.5±0.2 mm may be used, with the embodiments of the closureof the present invention providing the compatible overall length for usewith current automated handling systems and NMR spectrometers.

Embodiments of closures or caps and NMR tubes as described before may bemarketed as NorLoc™ Caps and Norell® NMR Tubes. A description of theseenclosures, caps and related NMR tubes can be found in U.S. Pat. No.8,054,080 to Norell issued on Nov. 8, 2011, which is incorporated hereinby reference in its entirety.

A further improvement of an NMR cap design is provided next as anembodiment of the present invention. In addition to the elementsdescribed above and in accordance with an aspect of the presentinvention an internal sealing band or constriction is added that alsofunctions as a locking or retaining element when used in conjunctionwith specially modified NMR tubes. This new feature is called the“secondary locking seal” hereafter.

The new “secondary locking seal” cap also works with unmodified NMRtubes, however, without offering the further benefits of the “secondarylocking seal.” The NMR tubes may be specially modified versions of anNMR tube as disclosed earlier herein, by adding and accuratelypositioning a band of a defined thickness around the outer diameter ofthe NMR tube. The band may be a band or ridge of material that is addedon a predetermined position partially or completely around thecircumference of the NMR tube. The band may surround the outer diameterof the NMR tube completely or it may surround it partially.

In one embodiment of the present invention, the band may also surroundthe outer diameter of the NMR tube partially, leaving at least one partof the circumference of the NMR tube uncovered. In a further embodimentof the present invention the band is attached around the NMR tube withat least two breaks or parts of the NMR tube being uncovered.

Accordingly, one can modify already manufactured NMR tubes by adding aband, preferably by a machine with high precision and a high throughput,to NMR tubes, to enhance use of caps with a “secondary locking seal” asdescribed further below. The band has a thickness that is appropriate towork as a seal in combination with one or more added features in thecap.

In accordance with an embodiment of the present invention, a systemsolution is provided for a combined NMR tube with cap with “secondarylocking seal” wherein a permanent feature is added to the NMR tube thatis a surrounding ridge or band of material around the exterior of theNMR tube at a predefined location of the NMR tube. In accordance with anaspect of the present invention a band is printed, by for instancescreen printing, on the NMR tube. The NMR tube may already have beenprovided with some pre-printed feature that is used to align the NMRtube for very precise location to print the desired band. To preventoverlap of printed ink, a small gap may be left between the two ends ofthe band. Ink that is used may be of any type that can strongly adhereto glass. In some embodiments, a two component epoxy based screenprinting ink may be used. By way of non-limiting example, any ink andcatalyst in the Enthone 50-Series CAT-L-INK Technical data sheet issuedJan. 30, 2008, may be used. The Enthone 50-Series CAT-L-INK Technicaldata sheet issued Jan. 30, 2008, is herein incorporated by reference inits entirety.

The printed band may have a thickness that is proportional or the sameas a silk screen used to deposit the material. In one or moreembodiments, the thickness of the material deposited on the NMR tube maybe in the range of 0.0002 to 0.0014 inches thick. In other embodiments,the material deposited on the NMR tube may be 0.00025 inches thick.

The band may have a width in the range of 0.005 to 0.180 inches. Inother embodiments, the band of material may have a width of 0.028inches. In yet other embodiments, the band may have a width of 0.028inches centered at a distance of 0.144 inches from the open end of anNMR tube, the locking ring partially encircling the NMR tube, having onediscontinuous segment, and one continuous segment having one or morelinear lengths of 0.512 inches or 0.315 inches.

In one or more embodiments, the pattern of the printed band may bediscontinuous, consisting of segmented lines or bands having 1, 2, 3 ormore breaks or discontinuities. In one or more embodiments, the lengthsof the discontinuous regions can range from 0.005 to 0.303 inches. Inother embodiments, the printed band may consist of round, square orrectangular “dots” or other geometric shapes of varying size, in therange of 0.005 to 0.180 inches, separated by distances in the range ofabout 0.005 to 0.303 inches. In one embodiment, the printed band ismostly continuous, having only one break or discontinuity of about 0.103inches in length.

Printing by way of screen printing of the band on the NMR tube is knownand relatively inexpensive and fast. However, other methods ofdepositing a band on the outside of the NMR tube are also contemplated,including the application of pre-made decals supplied by, for example,Pedco-Hill, Inc. in Warminster, Pa. 18974. Pre-made decals can beaffixed to glass surfaces by first moistening the decal with water,positioning the decal on the glass surface, allowing the decal to airdry followed by permanently fusing the decal to the glass surface byheating at about 1000° F.

Referring to FIG. 9, the secondary locking seal is added into the distalsection 22 of the hollow bore 20 at a sufficient distance within toleave a remainder of distal section 22 intact at the immediate entranceto hollow bore 20. This is illustrated in FIG. 9 wherein first distalsection 227 will be modified to add the secondary locking seal andsecond distal section 228 will be left unmodified. First distal section227 and second distal section 228 together form distal section 22. Thisis further illustrated in FIGS. 10 and 11. One can see that first distalsection 227 has been provided with a tapered opening, wherein the insidediameter of the enclosure 10 diminishes when viewed from the beginningof the opening moving to interference 24 and proximal end 26. FIG. 11shows first distal section 227 in greater detail marked as “Detail C”.

Though, in one or more embodiments, the length of distal section 22 hasbeen reduced to a range of 0.008 to 0.025 inches, and in otherembodiments may be reduced to a length of 0.015 inches, it neverthelessremains discernible to the end user as a functional element, guiding andaligning the NMR tube into hollow bore 20 when placing a newly designedand structured NorLoc™ cap onto the NMR tube, thereby incorporating theinventive features. The secondary locking seal is preferably locatedwithin the new NorLoc™ cap at the point of maximum flexibility, i.e., atthe point of minimum wall thickness found at the extreme end of thedistal second portion 18 that is opposite to the proximal first portion16, and away from any restraining or reinforcing features such as theclosed end of proximal first section 16.

The first distal section 227 transitions into second distal section 228with a relatively sharp ramp 230. The angle of ramp 230 with a normalonto a straight wall of the outside of the NMR tube or an angle with aline parallel to axis X as shown in FIG. 1 is preferably as close aspossible to being perpendicular or 90 degrees. For some purposes, suchas manufacturing a 90 degree angle may not be possible. More preferablyis an angle of 85 degrees or greater. Most preferably is an angle of theramp that is not smaller than 75 degrees. This allows the first distalsection 227 of the enclosure to capture or hook with the ramp 230 thelocking ring 123.

The increased flexibility of the cap at this point permits the secondarylocking seal to fit over the corresponding NMR tube diameter much moretightly (in other words, the inside diameter of the secondary lockingseal within the cap can be made much smaller) and still allows the enduser to easily place the cap onto the NMR tube. For example, the insidediameter of the secondary locking seal in a 5 mm cap can be reduced to4.50 mm-4.78 mm and still easily slip onto a 5 mm NMR tube of nominal4.97 mm outside diameter.

As a further result, the inside diameter of the cap within the centralsection 24 of hollow bore 20, exhibiting a compliant interference fitthat constitutes the primary seal, can be enlarged slightly, therebyalleviating the sometimes difficult process of applying or removing thecap experienced by some end users. In summary, this embodiment of theNMR cap seals even more effectively than the design provided earlierabove while increasing ease of use.

To further safeguard the integrity of the assembled cap and NMR tubecombination, a special element can be added to the NMR tube, consistingof a screen printed band or ring encircling the outside circumference ofthe NMR tube, hereafter referred to as the “locking ring” as alreadydescribed above. See element 123 in FIG. 12.

FIG. 12 illustrates an NMR tube 14 in one embodiment of the presentinvention. A marking area 121 is reserved for printing or marking thetube with relevant information. Part of the marking is a straight area122 across the width of the NMR tube that marks a specific height of theNMR tube when placed in a vertical orientation. Because the line 122 isexactly defined it is possible to print the locking ring 123 on apredefined distance from 122. Exact positioning is of an NMR tube isimportant, as one wants the feature 230 in the cap to correspond withthe locking ring 123 on the NMR tube.

Referring to FIG. 11, the sharp innermost (or proximal) edge of ramp 230of the secondary locking seal has a nearly perpendicular profile to thecentral axis X through hollow bore 20, and so can engage the raisedscreen printed edge of the locking ring on the NMR tube as it passesover and beyond the locking ring upon proper cap placement, therebyadding additional resistance to cap removal.

In contrast, the outermost (or distal) edge 231 of the secondary lockingseal within the cap has a gently tapered profile, offering minimalresistance to cap placement by virtue of the gently tapered surfaceencountered by the locking ring during cap placement.

The locking ring must be precisely positioned at the correct distancefrom the open end of the NMR tube to fulfill its purpose, and when thecap is correctly placed on the NMR tube, the locking ring is notvisible, but is hidden within the cap. For this reason, the adjacentmarking area or label patch 121 also is a structure that has afunctional purpose in addition to what might be considered merelydecorative or aesthetic markings. The end of the marking area 122adjacent to the open end of the NMR tube has been specially designedinto a straight band or line that fully or partially encircles the NMRtube, forming a reference line that indicates full and correct placementof the cap when the base of the cap contacts the reference line. At thispoint, the locking ring, hidden from view within the cap, will also bepositioned correctly in relation to the cap to properly engage theproximal edge of the secondary locking seal within the cap.

In order for these new screen printed features to work effectively, theprint screens must be accurately made and the image precisely printed onthe NMR tube to maintain accurate positioning of the marking area inrelation to the locking ring, which in turn must be accuratelypositioned relative to the open end of the NMR tube in FIG. 12.

Purpose and Benefits

The design of the cap, as provided earlier above, having only theprimary seal formed by the compliant interference fit of central section24, sealed and contained most common NMR solvents very effectively,including highly volatile solvents such as acetone-d6 or chloroform-d.However, the tight but effective seal also may cause difficulty for someend users, especially when attempting to remove the cap. Ambienttemperatures below normal room temperature may further aggravate andcompound this difficulty.

In an effort to ease potential difficulties in the process of capremoval, the inner diameter of the cap within the central section 24 ofhollow bore 20 is enlarged. This change eases cap placement and removal,but another problem may arise as a result of this change.

After a few hours of exposure to certain solvents contained within theNMR tube, primarily chlorinated solvents such as chloroform ordichloromethane (methylene chloride) and to a lesser extent acetone, thesolvent vapors could permeate into the polyethylene polymer material ofthe cap and swell or enlarge the cap to a slight degree, which may causea nearly complete loss of retention of the cap to NMR tubes having anouter diameter near the lower end of the size range.

This is a deficiency common to polyethylene resins in general (includinglow density polyethylene, or LDPE, that is used to make caps) and canresult in separation of the cap from the NMR tube, especially during,but not limited to, unattended NMR analyses of multiple samplesconducted using automated robotic sample handling systems that handlesamples by means of the cap only, and not by the NMR tube. This type ofcap failure can cause expensive NMR instrument damage as well as loss ofexpensive samples, such as certain natural products that requireextensive effort to collect and concentrate a sufficient, but verylimited amount, of pure sample for analysis.

It was found that the amount of swelling or enlargement of the diameterof a 5 mm cap may be about 0.13 mm at maximum, reaching an equilibrium,or steady state, upon prolonged exposure to the solvent vapors. Assolvent vapors permeate into and then saturate the polyethylene polymer,a steady state condition eventually occurs when solvent vapors begin topermeate completely through the cap to the exterior and escape from thesystem, thereby effectively limiting the amount of absorbed solventvapor and consequent further swelling or enlargement of the polyethylenepolymer.

This is a purely physical (not a chemical) and completely reversibleprocess. The chlorinated solvents and acetone mentioned earlier, as wellas most other common NMR solvents, do not chemically react withpolyethylene, causing polymer modification or degradation, but rather,upon cessation of exposure to solvent vapor, the vapor previouslyabsorbed into the polyethylene cap material is eventually completelyexpelled. This process can be hastened by gentle heating, especially ina vacuum oven at reduced pressure, restoring the cap to its originalsize and condition.

However, because of the many otherwise outstanding attributes of lowdensity polyethylene (LDPE) that may be used to make a cap, it remains amaterial of choice for NMR tube caps and other closures of all kinds,not only because of its inherent optimum degree of flexibility andelasticity, but also because LDPE possesses excellent resistance tochemical degradation and attack, is low in cost and can be easily andaccurately injection molded in large quantities.

The positive aspects of LDPE remain so attractive, in fact, that thesusceptibility to chlorinated solvents is largely tolerated orcircumvented by most NMR spectroscopists by limiting the exposure time,replacing the exposed caps with new ones immediately prior to analysisin the NMR instrument and/or using a much more expensive cap materialsuch as PTFE (polytetrafluoroethylene) as recommended in the industry.These restrictive measures still constitute a stumbling block for manyNMR end users, however, so a permanent remedy would be widelyappreciated.

The addition of the secondary locking seal as illustrated in FIGS. 10-11augments the sealing function of the compliant interference fit ofcentral section 24 of hollow bore 20 in the cap provided as for instanceillustrated in FIG. 5. It also permits a lessened amount of interferenceto be incorporated into central section 24, thereby improving safety andease of use by reducing the amount of effort required to fit or removethe cap to and from the glass NMR tube, while simultaneously preservingand enhancing the barrier function of the earlier design of the capprovided herein by preventing loss of expensive NMR samples and solventsdue to evaporation from within the sample, or ingress of ambientcontaminants such as atmospheric moisture and oxygen from without. Theinterference can be lessened by about 0.002 inches.

The tighter fitting, decreased inner diameter of the secondary lockingseal, made possible by virtue of its placement within the most flexibleportion of the cap, as explained previously, leaves ample margin tocounteract the loss of retention of the cap to the NMR tube, caused byexpansion or swelling of the polyethylene cap material (LDPE) whenexposed to certain, primarily chlorinated, NMR solvents, but withoutsacrificing ease of placement and removal from the NMR tube.

The above mentioned benefits of this new design of the cap can berealized in combination with most conventional NMR tubes of matchingnominal diameter. However, using the new caps in combination withspecially designed and precisely screen printed NMR tubes having the newlocking ring element as illustrated in FIG. 12 adds a measure ofadditional physical cap restraint, increasing reliability bysafeguarding against cap and NMR tube separation when used inpotentially high stress applications, such as unattended robotic sampletransfer and handling of multiple samples containing even problematicchlorinated solvents. For instance, deuterium labeled (also known asstable isotope labeled) solvents commonly used in NMR spectroscopy,including, but not limited to, chloroform-d and dichloromethane-d2(methylene chloride-d2) as well as other less common solvents such asdichloroethane and trichloroethane. Also, acetone-d6, though not achlorinated solvent, is commonly used in NMR work and can cause caploosening as well.

Data

In accordance with an aspect of the present invention, NMR tubesprovided with and without a locking ring of the present inventioncontaining a solution of chloroform-d (CDCl₃) were tested for theability of a cap, with or without a secondary locking seal of thepresent invention, to maintain seating on the open end of a tube overthe course of 50+ hours. Chloroform-d is a common stable isotope labeledsolvent used extensively in NMR spectroscopy (the properties ofchloroform-d are very similar to standard, or non-labeled chloroform).The interior surfaces of the caps were exposed only to chloroform-dvapor (not liquid solvent) contained within the headspace of the cappedNMR tubes, for the specified time period shown in the table.

To test the retention of the cap to the NMR tube, a very light pull wasmanually applied with light incidental shaking to the capped NMR tube,while holding only the cap. When this action was performed, the cap andtube were aligned vertically. Thus the approximate amount of downwardforce applied to the tube was approximately proportional to the mass ofthe tube and gravitational acceleration on earth; i.e. F=m*g (where F isthe force of gravity; m is the mass; and g is 9.8 m/s{circumflex over( )}2). Thus, for a NMR sample tube that weighs approximately 2.13grams, the gravitational force is about 0.0208 N. This action was tosimulate the types of forces commonly applied to the NMR tube and capduring normal use. The cap and NMR tube were evaluated for whether oneseparated from the other.

The data in the table below was obtained by testing 5 mm NMR tube capsof the indicated design over the time frames indicated. The averageincrease of internal cap diameter as a result of exposure to thevolatile solvent is also indicated below.

TABLE 1 Table Showing Cap Retention After Exposure to Chloroform-d(CDCl₃) Vapor Time (hours) Longer 0.5 1.0 1.5 2.0 3.0 4.0 5.0 6.0 24 50(8 weeks) % Average 0 0 0.16 0.26 0.52 0.78 0.93 0.93 1.45 1.45 1.45Increase of Cap Internal Diameter Traditional Cap YES YES NO NO NO NO NONO NO NO NO w/ Traditional Tube (Does cap stay on?: YES/NO) New LockingYES YES YES YES YES NO NO NO NO NO NO Seal Cap w/ Traditional Tube (Doescap stay on?: YES/NO) New Locking YES YES YES YES YES YES YES YES YESYES YES Seal Cap w/ Locking Band Tube (Does cap stay on?: YES/NO)

The “traditional” NMR tube cap used in the above experiment was the NMRcap shown and described in U.S. Pat. No. 8,054,080, the entirety ofwhich is herein incorporated by reference, which is the closest knownNMR tube cap design to the present invention. The new locking seal capand locking band tube used in the experiment were as shown and describedabove. The “traditional” NMR tube was without any locking band, or otherscreen printed design, on the outside of the tube.

As is apparent in the data above, the new locking seal cap has superiorretention properties when used alone or in combination with locking bandwhen compared to the traditional NMR tube cap. After 1.5 hours ofexposure to chloroform-d, the inner diameter of caps increases by anaverage of 0.16%. At that time of exposure, the traditional NMR tube capis no longer able to maintain seating on the traditional NMR tube underthe conditions of normal use (See Table 1). By contrast, the new lockingseal cap is able to maintain seating on the traditional NMR tube for upto 3 hours of exposure to chloroform-d (See Table 1). Thus, the newlocking seal cap has a 100% improvement in retention with thetraditional NMR tube, effectively doubling the time a cap can be exposedto solvent before retention problems occur.

When the new locking cap is combined with an NMR tube with the newlocking band, the improvement in retention is even more dramatic. Thecurrent data suggests that the locking seal cap will remain seated onthe locking band tube under normal handling conditions indefinitely. Asshown above, even after eight weeks of exposure to chloroform-d, withthe increase in cap diameter plateauing at 1.45%, the locking seal capis retained on the locking band tube under normal handling conditions(See Table 1). Thus, the current data shows that the locking seal cap isable to maintain seating on the locking band tube at least 896 timeslonger than the traditional cap on a traditional tube (See Table 1).Thus, the problem of losing cap retention after exposure to solvents maybe virtually eliminated by using the locking seal cap and locking bandtube as shown and described above.

The data in the above table was derived by testing 5 mm NMR tube caps. 3mm NMR tube caps are initially more resistant to chloroform exposure andsubsequent loss of retention, but reach a comparable state of expansionfollowing an additional exposure time of about 2 hours.

Below are 2 tables for 5 mm and 3 mm NorLoc™ caps, respectively,modified in accordance with the present invention showing the measuredincrease of the cap inner diameter (ID) after exposure to chloroform-dvapor for the specified periods of time. The caps were not permitted tocontact liquid solvent, but all surfaces, both inside and out, wereexposed to a saturated atmosphere of solvent. In this respect, thefollowing tests differ slightly from those in Table 1 where only theinterior surfaces of the caps were exposed to solvent vapor containedwithin the capped NMR tubes.

TABLE 2 ID Expansion of 5 mm NorLoc ™ Caps Upon Exposure to Chloroform-d(CDCl₃) Vapor Initial ID Measurement In Decimal Inches After SpecifiedExposure Time Sample ID, (measured with pin gauges) Number in 0.5 hr 1.0hr 1.5 hr 2.0 hr 3.0 hr 4.0 hr 5.0 hr 6.0 hr 24 hr 50 hr 1 0.193 0.1930.193 0.194 0.194 0.1945 0.195 0.196 0.196 0.198 0.198 2 0.193 0.1930.193 0.193 0.193 0.1935 0.194 0.194 0.194 0.194 0.194 3 0.193 0.1930.193 0.193 0.1935 0.194 0.1945 0.1945 0.1945 0.1955 0.1955 Average0.193 0.193 0.193 0.1933 0.1935 0.1940 0.1945 0.1948 0.1948 0.19580.1958 % N/A 0 0 0.16 0.26 0.52 0.78 0.93 0.93 1.45 1.45 Average IDIncrease

Test samples were red color LDPE Closed Port caps suspended in a closedvessel above liquid chloroform-d (CDCl₃) to permit exposure to vaporonly.

TABLE 3 ID Expansion of 3 mm NorLoc ™ Caps Upon Exposure to Chloroform-d(CDCl₃) Vapor ID Measurement In Decimal Inches After Specified ExposureTime Sample Initial (measured with pin gauges) Number ID, in 0.5 hr 1.0hr 1.5 hr 2.0 hr 3.0 hr 4.0 hr 5.0 hr 6.0 hr 24 hr 50 hr 1 0.113 0.1130.113 0.113 0.1135 0.1135 0.114 0.114 0.1145 0.117 0.117 2 0.114 0.1140.114 0.114 0.114 0.114 0.114 0.114 0.115 0.1185 0.1185 3 0.113 0.1130.113 0.113 0.1135 0.1135 0.1135 0.114 0.1145 0.1175 0.1175 Average0.1133 0.1133 0.1133 0.1133 0.1137 0.1137 0.1138 0.114 0.1147 0.11770.1177 % Average N/A 0 0 0 0.35 0.35 0.44 0.62 1.24 3.88 3.88 IDIncrease

Test samples were red color LDPE Closed Port caps suspended in a closedvessel above liquid chloroform-d (CDCl₃) to permit exposure to vaporonly.

The data represented in Tables 2 and 3 show that there is an expansionof the internal diameter of both 5 mm an 3 mm traditional Norloc capsafter exposure to chloroform-d vapor. In both cases, the increase ofinternal diameter plateaus after approximately 24 hours of exposure tosolvent vapor.

Screen Printing Material

One or more embodiments of the present invention may comprise a materialdeposited on the outer surface of the NMR tube. This material may be anepoxy-based two component, permanent ink such as Enthone® 50 SeriesCat-L-Ink (manufactured by Enthone, Inc., New Haven, Conn. 06508), orany other material that has strong adhesion to glass. The technical datasheet for Enthone® 50 Series Cat-L-Ink issued Jan. 30, 2008, is hereinincorporated by reference in its entirety. The color of the materialdeposited on the surface of the NMR tube may be any one of: white, whitematte, hi-hide white; lemon yellow; medium yellow; orange; emeraldgreen; deep green; ultramarine blue; light blue; deep red; medium red;chocolate brown; black; black matte; black gloss; clear gloss; clearmatte; among others.

The predominant component of the material is the ink base, which ismixed with a catalyst component followed by heat curing to facilitatehardening. For example, the catalyst component may be Enthone® CatalystNumber 9 (manufactured by Enthone, Inc., New Haven, Conn. 06508). Thecatalyst is composed of tetraethylenepentamine (40-50% w/w) in a solventof ethylene glycol butyl ether (40-50% w/w). Catalyst Number 9 is a heatcure only catalyst possessing good anti-yellowing resistance, especiallywhen in combination with a white color ink.

One or more embodiments of the deposition material may further comprisea solid filler material or flatting agent used to impart a matte finishand/or increase the coefficient of friction of the NMR tube surface.This material may consist of very finely powdered (generally known asfumed or colloidal) silica (silicon dioxide), such as SIPI414 Cabosil®pigment, a type of fumed silica.

Various aspects of the present invention employ a liquid mixture of ink,catalyst, and silica that may be applied by a screen printing processusing, specifically, “The AUTO-PAK™ Automatic Cylindrical Screen ProcessPrinter” (manufactured by Joseph E. Podgor Co., Inc., 7551 CentralHighway, Pennsauken, N.J. 08109) followed immediately by passage on achain conveyor system through an oven with temperature control of ±5° F.The thickness of the screen will determine the thickness of thedeposited material. In one or more embodiments the thickness of thedeposited material is in the range of 0.0001 to 0.0004 inches, or in therange of 0.0002 to 0.0003 inches, or approximately 0.00025 inches. Inother embodiments, the thickness of the deposited material will be0.0001 to 0.0014 inches.

Various embodiments of the invention may employ a deposited materialcomprising the following components in the following ranges:

Possible Range of Values Component (in percent by weight, % w/w) Ink70.0-97.0 Catalyst  3.0-10.0 Fumed Silica Filler  0-20

In other embodiments, the values (in percent by weight, % w/w) may beapproximately 93.8% ink, 3.6% catalyst, 2.6% fumed silica filler. Inother embodiments, the curing agent may be 5.0% or 5.1% w/w.

In various embodiments, the AUTO-PAK™ screen printer may be used asoriginally supplied by the manufacturer, or may be used with anadditional length of custom built oven added (e.g. approximately 12feet). The curing oven length may be adapted to achieve the minimumexposure time (residence time) necessary at a desired printing speed toheat and cure the freshly applied catalyzed epoxy ink to a predetermineddegree of hardness.

One or more embodiments of the invention may employ material depositedon an NMR tube and cured at a temperature below 300 degrees F. At suchtemperatures, the color of the ink does not change to a degree that isperceptible to the human eye. In some embodiments, the depositedmaterial may be cured at a temperature of 250 degrees F. forapproximately 3 minutes, causing no perceptible color change of the ink,followed by continued curing at room temperature for several hours. Toverify the absence of any yellowing of white ink, or color changes inany of the other various color inks, a simple visual comparison may bemade between the test sample and a reference standard, such as a pieceof white paper or a previously screen printed NMR tube deemed to beacceptable. Alternatively, colors, including varying shades of white,can be quantified using instruments such as a tristimulus colorimeterwhich measures the CIE XYZ Color Space Tristimulus Values (See e.g., J.Soc. Cosmetic Chemists, 19, 649-667 (Sep. 16, 1968) which isincorporated by reference in its entirety). Alternatively, the absolutespectral reflectance or transmittance of a sample may be determinedusing a spectrophotometer. One or more of these methods may be used toconvert the spectral measurements to a standard reference colorcontained in the Pantone® Color Guide, which is can be used as areference for color comparison or verification, the entirety of which isherein incorporated by reference. In one or more embodiments of theinvention, the difference in tristimulus values of a CIE color of thecured ink relative to a reference standard may be less than 50%, lessthan 25%, less than 10% or less than 1%.

Placement of Material on NMR Tubes

One or more embodiments of the present invention may employ materialdeposited on an NMR tube at a position where contact is made withanother object. In this manner, the deposited material may enhanceretention of the object on the NMR tube during normal use. For example,as shown in FIGS. 16-18, NMR tubes are often inserted into spinnerturbines 400 prior to and during measurement of NMR spectra. Thesespinner turbines 400 define a hollow bore, through which the NMR tube isinserted. As some position within the hollow bore, some part of theturbine protrudes 460, narrowing the hollow bore, thereby contacting or“griping” the NMR tube. While the NMR tube is placed in the turbine, thecontacting or gripping parts 460 of the turbine are intended to retainthe tube at the desired position in the turbine during use in the NMRmachine. However, it is possible for the tube to change positionrelative turbine by slipping, and in some cases the tube may slip out ofthe turbine. This problem is compounded by the fact that the NMR tubeneeds to be placed in a particular position relative to the turbine tooptimally obtain NMR spectra. Thus, there is a need for an NMR tube thatcan both prevent slippage of the tube in the turbine and that can bequickly and simply placed at an optimal position relative to theturbine.

Various turbines contact the NMR tubes at certain positions along theNMR tube length. One or more embodiments of the present invention mayemploy deposited material on the outer surface of the NMR tube at aposition where contact with the turbine is made, with the depositedmaterial having a frictional coefficient higher than glass. In thismanner, various embodiments of NMR tubes may have regions of materialwith higher frictional coefficients, reducing the chance that a spinnerturbine may unintentionally slip off the NMR tube.

By way of non-limiting example, FIGS. 13-15 illustrate variousembodiments of the invention showing placement of material deposited inbands centered around turbine contact points. Each of FIG. 13-15 showthe position of a band of material deposited on a 7 inch NMR tube, witheach band centered on a contact point for a particular turbine. Forexample, according to one embodiment of the invention, FIG. 13 showsplacement of the center of bands at 2.7755 inches above the bottom(closed end) and 4.5465 inches above the bottom (closed end) of thetube, centered on the contact points for the 3 mm tube and 5 mm tubeBruker turbine. As shown in the figure the bands have an approximatewidth of 0.669 inches and are solid, so as to cover the minimum andmaximum (optimal) NMR tube depth while inserted in the turbine. However,in various embodiments of the invention, the bands may be wider than orless wide than the minimum and maximum tube depth as shown in thefigures. For example, the width of the bands may be less than 3 inches,less than 2 inches, less than 1 inch, or less than half an inch. Also,while the NMR tube represented in FIG. 13 comprises two bands, variousembodiments of the invention may comprise one band or more than twobands. Furthermore, while FIG. 13 shows the exemplary bands as beingsolid, various embodiments of the invention may comprise continuous ordiscontinuous bands, comprised of various shapes, patterns, orcharacters. The bands deposited in the various embodiments may cover theentire circumference of the tube or may cover only part of thecircumference of the tube. For example, in one or more embodiments, thematerial may cover more than ⅙ of the tube circumference, more than ¼ ofthe tube circumference, or more than ½ of the tube circumference.

As shown in FIG. 14, a single band is placed on the NMR tube at thepreferred contact point for the 5 mm JEOL turbine. This contact point islocated along the length of the NMR tube at approximately 5.75 inchesfrom the bottom (closed end) of the tube. Similarly, as shown in FIG.15, a single band is placed on the NMR tube at the preferred contactpoint for the 5 mm Agilent/Varian Turbine. This contact point is locatedalong the length of the NMR tube at approximately 6.25 inches from thebottom (closed end) of the tube.

In addition to the deposited material acting to prevent the NMR tubefrom slipping out of the turbine, one or more embodiments of the presentinvention may use the deposited material as a reference mark for properseating of the NMR tube in the turbine. For example, in someembodiments, one or more bands of deposited material may have an edgethat indicates the optimal position of the tube in the turbine, whichcan be manually aligned with the top or bottom edge of the turbine bythe user. This feature will allow the user to properly position the NMRtube in the turbine without having to use an external depth gauge.Alternatively, part of one or more bands of deposited material may havea distinct visual appearance (such as color or pattern) that wouldindicate where the top or bottom edge of the turbine should be inrelation to the tube. For example, within a band of deposited material,an additional distinctly colored band may be present, indicating to theuser where the top of the turbine should be aligned. In yet furtherembodiments, the proper positioning of the turbine may be indicated by achange in texture from glass to deposited material that can be felt bythe user as the tube is slid into a turbine. For example, the transitionpoint from glass to deposited material may be positioned such that theedge touches the contacts (or grippers) of the turbine at a point thatplaces the turbine in the optimal position relative to the tube. In thismanner, the user would be able to feel (by tactile sensation) when thetube is slid into the optimal position relative to the turbine.

In further embodiments of the present invention, the width of a band ofdeposited material may indicate a range of insertion depths of the NMRtube relative to the turbine, from a minimum to a maximum. For example,one or more deposited bands may be 0.669 inches wide with the edgeclosest to the open end of the tube indicating the maximum (optimal)depth and the edge closest to the closed end of the tube indicating theminimum depth. Thus, the top 470 or bottom 480 edge of the turbine mayfall anywhere inside the one or more bands of material 490, indicatingthat the tube is in an acceptable position relative to the turbine. Seee.g. FIGS. 16-18.

In further embodiments of the present invention, two or more bands ofmaterial may be deposited on an NMR tube relative to each other. Forexample, as shown in FIG. 13, one embodiment of the invention maycomprise two bands, each band having two edges, with each of the topedges of the two bands, and each of the bottom edges of the two bandsbeing a distance of 1.772 inches apart.

In yet other embodiments, bands of fixed distance between each other maybe positioned to contact one or more gripping parts of a turbine. Forexample, turbines the distance and positioning of material deposited ona NMR tube may be adapted to contact the appropriate gipping parts ofthe turbine on a 4 inch NMR tube.

Any of the above described features may be used in combination with oneanother. For example, any combination of bands of material deposited onthe surface of the NMR tube to enhance gripping of the turbine may beused along with the new NMR tube locking seal cap and band. A single NMRtube, according to the present invention, can include any of the bandsor printed areas described herein. Further, any of the bands can use anyof the various ink based compositions described herein. Thus, forexample, an NMR tube can include areas 121 and band 123 (FIG. 12) aswell as bands meant to interface with a turbine, such as those show inFIG. 13. Each of these bands can be printed on the NMR tube with thesame ink-based composition or each can be printed with a different incomposition.

An NMR tube, such as the one disclosed in FIG. 13, and a turbine, areused together in accordance with an aspect of the present invention. Asis conventional, the NMR tube is inserted into the turbine. According tothe method, the first band on the NMR tube (the band closer to theclosed section of the NMR tube) is fully inserted into the turbine.Thus, the NMR tube is pushed until the first band disappears. Then, theNMR tube is further inserted into the turbine until the top part of thesecond band is visible, but the other part of the second band is hiddeninside the turbine. The two bands on the NMR tube are spaced apart by adefined amount, as previously described. The turbine interfaces with theNMR tube at two points, the two points being separated by the definedamount. Thus, when the NMR tube is inserted into the turbine such thatthe top part of the second band is visible, the bands on the NMR tubeinterface with the turbine. This interface provides a significantlyimproved grip on the NMR tube by the turbine and prevents the NMR tubefrom sliding out of the turbine.

While the invention has heretofore been described with certain degreesof particularity, there are countless configurations for the NMR tubeand cap of the present invention. FIG. 1 through FIG. 18 illustrate onlya few possible configurations, and in no way should be construed aslimiting the application of the inventive apparatus to thoseconfigurations. To the contrary, the invention is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims. The scope of the followingclaims is to be accorded the broadest interpretation so as to encompassall such modifications and equivalent structures and functions.

What is claimed is:
 1. A method for securing a cap to a sample tube, themethod comprising: providing a tube having an open end portion and aclosed end portion, and a cap including a bore defining a central axis,the bore including a distal portion defining an open distal end of thebore, and an opposite proximal portion defining a closed proximal end ofthe bore; inserting the open end portion of the tube through an entranceportion of the open distal end of the bore; slideably engaging the openend portion of the tube with a first constriction portion of the bore,the first constriction portion having a first diameter less than anouter diameter of the open end portion of the tube; and subsequentlyslideably engaging the open end portion of the tube with a secondconstriction portion of the bore having a second diameter less than theouter diameter of the open end portion of the tube, the first and secondconstriction portions of the bore being axially spaced apart along thecentral axis; wherein the first and second constriction portions sealthe cap to the tube.
 2. The method according to claim 1, furthercomprising subsequently sliding the open end portion of the tube fartherinto the proximal portion of the bore after engaging the secondconstriction portion, the proximal end portion of the bore having adiameter greater than the outer diameter of the open end portion of thetube.
 3. The method according to claim 2, further comprising abuttinglyengaging the open end portion of the tube with a proximal end wall inthe proximal portion of the bore.
 4. The method according to claim 1,wherein the first constriction portion of the bore is disposed in thedistal portion of the bore, and the second constriction portion of thebore is disposed in an intermediate central portion of the bore betweenthe distal and proximal portions.
 5. The method according to claim 1,wherein the entrance portion of the open distal end of the bore has atapered section in which the diameter of the tapered section diminishesin moving from the open distal end of the bore towards the closedproximal end of the bore.
 6. The method according to claim 5, whereinthe tapered section of the bore has a distal-most diameter at the opendistal end of the bore which is larger than the outer diameter of theopen end portion of the tube, and a proximal-most diameter which equalsthe first diameter of the first constriction portion which is contiguouswith the tapered section.
 7. The method according to claim 1, wherein anaxial portion of the bore located between the first and secondconstriction portions of the bore has a greater diameter than the firstand second diameters of the first and second constriction portions ofthe bore.
 8. The method according to claim 7, wherein a locking ring onthe tube nests within the axial portion of the bore upon the cap beingfully seated on the tube so that the open end portion of the tube abutsagainst a proximal end wall in the proximal portion of the bore.
 9. Themethod according to claim 1, wherein the tube includes acircumferentially-extending raised locking band at least partiallyencircling the open end portion of the tube.
 10. The method according toclaim 9, wherein the raised locking band slideably engages the firstconstriction portion of the bore when sliding the open end portion ofthe tube through the first constriction portion.
 11. The methodaccording to claim 10, wherein the locking band is positioned betweenthe first and second constriction portions of the bore when the open endportion of the tube abuttingly engages a proximal end wall in theproximal portion of the bore.
 12. The method according to claim 11,wherein a proximal-most part of the first constriction portion includesa ramp defining a proximally facing locking surface orientedperpendicular to the central axis of the bore, the locking surfacepositioned to engage an edge of the locking band when the open endportion of the tube abuttingly engages the proximal end wall of thebore.
 13. The method according to claim 12, wherein a diameter of thebore adjacent to the locking surface is greater than an outer diameterof the locking band.
 14. The method according to claim 9, wherein thelocking band extends continuously around the open end portion of thetube.
 15. The method according to claim 1, wherein the firstconstriction portion of the bore comprises an annular protrusion of thecap extending radially inwards towards the central axis of the bore. 16.The method according to claim 1, wherein the second constriction portionof the bore has a greater axial length than the first constrictionportion.
 17. A method for securing a cap to a sample tube, the methodcomprising: providing a tube having an open end portion, a closed endportion and a circumferentially-extending locking band at leastpartially encircling an exterior of the tube, and a cap including a boredefining a central axis, the bore including a distal portion defining anopen distal end of the bore, an opposite proximal portion defining aclosed proximal end of the bore, and a central portion therebetween;inserting the open end portion of the tube through an entrance portionof the open distal end of the bore; slideably engaging the open endportion of the tube with a first constriction portion of the bore, thefirst constriction portion having a first diameter less than an outerdiameter of the open end portion of the tube; and subsequently slideablyengaging the open end portion of the tube with a second constrictionportion of the bore by sliding the tube farther into the bore, thesecond constriction portion having a second diameter less than the outerdiameter of the open end portion of the tube, the first and secondportions of the bore being axially spaced apart along the central axis;subsequently sliding the open end portion of the tube into the proximalportion of the bore by sliding the tube farther into the bore; andabuttingly engaging the open end portion of the tube with a proximal endwall of the proximal portion of the bore to fully seat the tube in thebore; wherein the first and second constriction portions seal the cap tothe tube.
 18. The method according to claim 17, wherein when the openend portion of the tube abuttingly engages the proximal end wall of thebore, the locking band nests within an axial portion of the bore whichis located between the first constriction and the second constriction,the axial portion of the bore having a greater diameter than the firstand second diameters of the first and second constriction portions. 19.The method according to claim 17, wherein the proximal end portion ofthe bore has a diameter greater than the outer diameter of the open endportion of the tube.
 20. The method according to claim 17, wherein thefirst constriction portion of the bore is disposed in the distal portionof the bore, and the second constriction portion of the bore is disposedin the central portion of the bore between the distal and proximalportions.
 21. The method according to claim 17, wherein a proximal-mostpart of the first constriction portion includes a ramp defining aproximally facing locking surface oriented perpendicular to the centralaxis of the bore, the locking surface positioned proximally of the firstconstriction to engage an edge of the locking band.
 22. The methodaccording to claim 21, wherein a diameter of the bore adjacent to thelocking surface is greater than an outer diameter of the locking band.23. The method according to claim 17, wherein the first constrictionportion of the bore comprises an annular protrusion of the cap extendingradially inwards towards the central axis of the bore.
 24. The methodaccording to claim 17, wherein the second constriction portion of thebore has a greater axial length than the first constriction portion. 25.The method according to claim 17, wherein an axial portion of the borelocated between the first and second constriction portions of the borehas a greater diameter than the first and second diameters of the firstand second constriction portions of the bore.